I have an issue with my car that I have been having for a while on and off. I have thought it to be lots of different things but now I believe I know what it is and possibly what is causing it. I would like to know if anyone else is having the issue and if so how they are curing it.
My issue is that after a fairly long drive when I turn the car off it doesn't want to run well at all, like it is running out of gas. If I keep it basically floored I can sputter around, but anytime I let off the gas it dies and is very hard to restart. When I check the fuel pressure when this is happening it is basically nothing and all that comes out of the check valve is a mist with a little liquid fuel. Once the car cools off long enough it has good fuel pressure and starts, runs, and drives fine. I just checked it this morning after having the issue again yesterday and I'm getting 40lbs pressure and after an hour of the car being off it is still holding at 25lbs.
So my guess as to what is happening is that the fuel is heating up excessively and eventually vaporizing turning from a liquid into a gas and obviously becoming much less dense. The thing I believe that is causing this is the fuel lines running as close to the catalytic converter as they do right after exiting the tank and before the fuel filter. My solution, since the car is registered in Wyoming, is to remove the cat and put in an "off-road" pipe thus removing the extremely hot cat from the equation.
Comments or thoughts? Am I way off or is there a different way to cure the issue? Will this even cure the issue? I would like to avoid using heat shields if possible because I hate fighting with those. Although now that I think about it, it seems like a heat shield there from the factory would make sense. I wonder if the previous owner removed one. Eventually I plan on running all AN lines for the fuel lines and if necessary putting heat socks over the length of them.
It is possible, my old truck stated boiling the fuel in the carb when they started adding alcohol in the gas. Alcohol has a lower boiling point. I had to add an insulated spacer. Try wrapping your fuel lines with insulation and see if the problem goes away. In theory fuel injection should not suffer vapor lock, however as they keep adding more alcohol it may start becoming more of a problem.
This can't be safe. If you really are vaporizing your fuel it is very close to the flash point. Compare it to a stock Fiero and fix what is missing or miss placed. The Las Vegas Fiero Club should be a great resource if you need it.
Check to make sure the check valve in the gas cap isn't sticking closed. If you evap/charcoal canister is working right and hooked up, make sure that filter on the bottom of it isn't packed full of dirt. If you are purging your canister and tank by vacuum and it has no way for fresh air to vent in, The tank builds up vacuum. Could be Try running with the cap loose. If that does it, Check Evap.
You stated the catalytic converter was heating up the fuel lines. If that is so, your lines or converter are not in the factory locations. My converter is on the drivers side of the engine while the fuel lines run up the passenger side. way to much space for the heat to transfer from that source. Now the exhaust manifold on the fire wall side comes the closest to the lines.
------------------ Mark ' 85 2m6 3.4PR In the Great Northwest!
The fuel pump is located in the tank. If the fuel in the line past the the fuel pump vaporized and you then depressed the valve, first vapor at 42 psu and then fuel at 42 psi would squirt out of the valve. Since nothing squirted out of the valve, my guess is the fuel pump wasn't running.
When you turn the key on, but just to on, does the fuel pump run for two seconds and then turn off? It should. This indicates the ECM/Fuel Pump Relay are supplying power to the fuel pump. Assuming the first test worked you should also be able to bump the starter and have the fuel pump turn on, and then two seconds later turn off.
GM also wired up a secondary way to power the fuel pump. It is the oil pressure switch. When cold if you crank the engine till it starts and the immediately turn it off, the fuel pump should run for a while, much longer than two seconds.
Anyways here's my guess. Your fuel pump relay has failed to operate, perhaps because the relay is bad, perhaps the socket is bad or perhaps the ECM circuit that powers the relay is bad. So that leaves the fuel pump running only on the oil pressure switch. It takes a little longer cranking for the oil pressure switch to close, but not so long when cold. When warm, the oil pressure isn't enough to turn on the switch and won't power the fuel pump.
More likely Bad pump and/or wiring etc to the pump... bad wiring and/or low fuel flow can cause a dead pump. A new pump w/ crap wiring will die soon. See my Cave, Electric Motors
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I agree of course with Ogre. It was common in carbed cars. I think its nearly impossible in a pressurized fuel injection system. FI has at least 40 pnds of pressure pushing it while carbed cars fuel pumps were only abut 6 pnds.
First of all I have to thank everyone for chiming in with suggestions. Now to respond to everyone.
The exhaust on this car is not stock, it has about 8 different welds on it in different places. I don't know what it is supposed to look like stock, but this one has definitely been worked on. The fuel lines on it are on the passenger side, however the cat is not on the driver's side, it is basically centered left to right and is about a foot long and because of that gets fairly close to the fuel lines. Without actually measuring it I'd guess it to be within six inches of the hard lines.
I took a look at the gas cap and it seems to be fine. I've never replaced it before though so I might as well get a new one. And see if that helps. At least it will eliminate that potential issue. I will take a look at the evap canister and see how the filter looks.
For all the fuel pump comments, I too have thought about this, but I'm hesitant to drop the tank because it's such a pain. I did buy a new pump just in case this one did go bad. The pump that is in the car is just over a year old being replaced in September of '13. Doesn't mean that it isn't possible for it to have gone bad. Things that I am fighting with myself about as to the pump is that it works fine when the car is cold. When I drove it home last night it started acting up just as I was getting home which was after about 45 minutes of diving. When I went out this morning it started up and ran fine for the 30 minutes or so of errands that I did. When I got home it was still running fine and when I put the pressure gauge on it it was at 39lbs and holding fine. I let it run another 20 minutes and no change so I turned it off. I don't know if driving for another 20 minutes would have caused a different result, but I would bet money that it would. When it is acting up it won't idle under load but usually will in neutral. The pressure gauge shows 1 or 2lbs of pressure is all even though I can hear the pump running. When I depress the purge it comes out as mostly a mist. Once I let the car cool off for an hour or so it will run 40lbs pressure and fuel is pure liquid when purged. Pump does prime normally when the key has been off for 10 seconds.
My question is why would the pump consistently work fine for a while and then stop at about the same time every day if it was good? Seems like too much of a coincidence. Also, why would it still be running when the car is acting up if it was bad? I guess at this point I'm hoping someone can tell me something that will convince me that even though the pump works normally for as long as it does, and even though I can hear it running when the car starts acting up, that the pump is still bad for some reason so I will be willing to drop the tank. What I'm trying to avoid is dropping the tank and no change in performance. I've dropped it 4 times in the last year and really want to avoid doing it anymore if not necessary.
[This message has been edited by mr_corean (edited 11-30-2014).]
Update, possible solution. I replaced the gas cap, no fix. Cleaned the filter on the bottom of the canister, still no fix. At this point I had a couple days off so I dropped the tank. Is it good or bad that I have gotten proficient enough at dropping the tank that I can replace a fuel pump in under an hour? Anyways, I pulled out the old pump and it looked and acted fine when bench testing it. I didn't really like it anyway though because it is a 340lph pump and would suck the sump dry when cornering or braking when the tank got low which resulted in the car dying. So I put the new pump in and went to test it before putting the tank back in and nothing. Had the daughter run the key for me while I tried finding out where the juice wasn't getting to the pump and found my issue, and hopefully the cause of all the issues I've been having. In the picture below the connector that passes from inside the tank to outside has been circled. On the inner portion the pins on it were corroded to the point that juice passed through them only occasionally and when it did it wasn't constant but sporadic. I cleaned that all up replaced the wires for the pump and the wire from the fuel sender to that connector and then reinstalled and voila! everything worked fine, including my fuel gauge that has never worked before. So far the issue seems to be sorted out. I'll report back in a few days after making some longer drives.
I have been reading posts about the tank for 5 years....and this is the first issue I have read about that specific connector. I wonder how many gauge problems are attributable to increased resistance in the connector.
Beats me. When I first got the car it didn't run and need a new fuel pump. When I replaced that I opened up the fuel sending unit and cleaned it all up trying to ensure that it would send a signal but couldn't get it to work. Once I replaced the wiring up in the connector the gauge worked fine. Makes sense the gauges won't work once the resistance in that connector goes up since it is a resistance based system.
Finally got the chance to make the longer drive today and of course the issue is not fixed. Fuel still becomes a gas after extended driving and no fuel pressure. Turned off the car and it wouldn't restart. When I turn the key the pump primes and then I go to start and it fires right away but dies right away as well. Doesn't even try to run. If I continue to crank the engine it just turns over and doesn't even try to run anymore until I turn the car off long enough to reprime the pump. One thing I noticed that I didn't notice before is that the car smokes pretty good while I'm cranking it if I try to keep cranking like described before. I sat for about two hours before it finally started up and ran like perfectly normal until about 5 minutes into the drive home. At that point I was on an interstate in 5th at about 70mph and it started surging and bogging continuously. I shifted into 4th running it higher into the RPMs and it ran normal. Shifted to 5th and same thing with the surging and bogging. Also when it was surging and bogging it threw a code but in 4th in the higher rpms that went away. When exiting the highway to get to the house it died on me but I was able to roll start it and keep the pedal mashed to get it the last couple blocks home. People on the way probably think I'm an absolute douche from the way the motor was wrapped up in order to keep it running. Got home and and went to restart and it is obviously dead and no fuel pressure. The codes that it is registering right now are 15, 23, 32, 33. Nothing will show when it is running fine, as in before it starts acting up. This sucks.
Anyways here's my guess. Your fuel pump relay has failed to operate, perhaps because the relay is bad, perhaps the socket is bad or perhaps the ECM circuit that powers the relay is bad. So that leaves the fuel pump running only on the oil pressure switch. It takes a little longer cranking for the oil pressure switch to close, but not so long when cold. When warm, the oil pressure isn't enough to turn on the switch and won't power the fuel pump.
Do you have 12+ volts at ALDL pin G when pump fails? That test point eliminates most wiring to the tank.
Back probe (use search) tank side of C502. Does that have same volts and see ground? C502 is on firewall goes to tank.
You have many splices at/in the tank that could cause problems. Ground goes to tubing looks like crap too.
If you bought new pump on Ebay, could be a counterfeit. Could be a bad new pump.
OE wiring, the pump will run on OP switch. Dying ECM/relay and no OP switch then low/no power to the pump.
The thing is that the pump never fails completely. I can hear it running the entire time. I haven't tested pin G when I'm not getting fuel pressure, but I will do that. I checked the volts at the ground inside the tank once it was all hooked up and after I cleaned up that connector mentioned previously and I was getting constant readings. The previous owner extended the wiring to the tank, and it definitely does not look pretty, but it seems to function just fine. I guess I could pull all that out and do a better job with it.
The pump is brand new AC Delco with stock flow rates from Autozone. I guess brand new doesn't mean it works necessarily, but it works fine when the car is cold. Like just now I drove it 5 miles to Autozone to pick up a couple more relays and it acts like nothing is wrong with it. The issue doesn't start until I drive it for extended periods, like 45 minutes or so. A quick stop doesn't reset that clock either. If I drive 30 minutes then stop for ten somewhere, the car will still start acting up on the 30 minute drive home.
By back probe do you mean just stick the wire with a probe?
Also, one more FYI, the car won't build up oil pressure when cranking. The oil pressure is fine when running, but it won't just build it up from the starter. Don't know if that helps is or is waste of space.
The vapor lock issuse usally only happens (here in Vegas) in the hot summer (yes phonedawgz, it does happen) BUT it doesn't happen when driving, only when it is a quick stop and you come out in like 5-10 mins. and usally it will only take up to a half hour to be able to restart. That all being said.
I know your car had all kinds of exhaust leaks, did you fix them all? As that will cause all kinds of heat issues. Being that it happens when driving I am thinking a leak may be causing the problem or the ICM is a problem. an overheated/bad icm will do exactly what is happing to you, (minus the vapor mist)
Also the PO did a bad hack job on too many wires on the car to count (he even used the same colors to extend everything for the readers FYI) now wires can get hot and pull out of plugs/sockets/crimps, then when cool go back into place. I would solder and heat shrink all the crimped splices the PO did, if I were you. Another test for this is either turn the key on, not start, and shake the harness everywhere you can and see if the pump kicks on and off, or when the car is running do the same shake test and see if it stumbles.
Otherwise get with me to make sure I am around and drive it untill it is bad and head to the shop and we can do as many tests as we can while it is bad in as short as time as possible. IE swap ICMs, check fuel pressure, check pump voltage, apply voltage to the pump, etc.
Sardonyx, I'm gonna hit you up sometime soon. I pulled back all the sheething around the wiring going to the relay and looks like the same crap we were dealing with with the AC. Total hack job as you put it.
